Vibration-proof incandescent halogen electric lamp for optical systems avoiding stray light



Nov. 24, 1970 P. STEI-NHART ETAL 3,543,078 VIBRATION-PROOF INCANDESCENT HALOGEN ELECTRIC LAMP FOR OPTICAL SYSTEMS AVOIDING STRAY LIGHT Filed June 11, 1.968

2 Sheets-Sheet 1 FIG-1 Paul Steinha t Josef Pfeifler INVENTORS By ATTORNE! Nov. 24, 1970 P. STEINHART ETAL 3,543,078

VIBRATION-PROOF INCANDESCENT HALOGEN ELECTRIC LAMP FOR OPTICAL SYSTEMS AVOIDING STRAY LIGHT Filed June 11. 1968 v 2 Sheets-Sheet 2 FIG-2 Paul Steinhart Josef Pfei ffc-r nwriumm BY AHORNFY United States Patent US. Cl. 313269 14 Claims ABSTRACT OF THE DISCLOSURE Incandescent halogen electric lamp with thin strapshaped molybdenum foil current in-leads projecting from proximity to the filament coil to and into the pinch of the lamp envelope for a considerable distance, secured and sealed therein and connected therein to terminal leads which pass to the exterior, the filament having straight end-reaches projecting laterally from the coil in direction longitudinally of the respective in-leads which, by corrugation or otherwise, are in re-enforcing surface juxtaposition thereto longitudinally of the filament end-reaches to and well within the pinch, with anchoring of the filament end-reaches being attained both by inclusion with the foil in-leads in the pinch and by latinum welds next to the ends of the foils proximate to the filament coil, the straight end-reaches of the filament beyond the foil inleads each having a length commensurate to but without materially exceeding the length of a diameter of the coil, thereby restraining the filament from emission of light in its straight end-reaches, and the re-enforcement for the filament end-reaches by the in-leads distributing vibrational deflection, thereby avoiding metal fatigue and breakage of the filament at a concentrated location.

PROBLEM AND SOLUTION INVOLVED Coil filament lamps are extensively used as headlights for automobiles and other vehicles, also as search-lights, spot-lights, projectors and elsewhere. Concentration of the light in a confined beam is augmented by use of a reflector with the filament at the focal point thereof. Stray light deviating from the concentrated beam is objectionable and is to be avoided as far as possible. One source of such stray light has been caused by incandescence of the straight end-reaches from the filament coil to the inleads, and various efforts have been made in the past to overcome the effects and/or derivation of this objectionable light. Up to the time of the present invention, no satisfactory solution of the problem has been attained. According to the present invention, a long-life lamp is obtained both by its mechanical improvement over the prior art and by giving due consideration to electrical and heat conduction, features which will appear in the more detailed description hereinbelow.

In the drawings:

FIG. 1 is an elevational view of a coil-filament halogen electric lamp showing one embodiment of the invention; and

FIG. 2 is a corresponding view of another embodiment of the invention.

DETAIL DESCRIPTION The present invention is involved with well-known construction of a tubular lamp envelope 1 composed of quartz Patented Nov. 24, I970 or other suitable hard glass, closed at one end by an exhaust tip 2 and at the other end by a pinch seal 3. According to the invention, longitudinally of said pinch seal and to the lamp axis, are molybdenum strap-shaped current in-leads 4, 5, constituting in this disclosure two thin parallel spaced-apart intermediate foil in-leads which extend well down into the pinch seal 3, said in-leads having a thickness approximating two hundredths of a millimeter (.02 mm.). Said in-leads project from the forward or upper end of the pinch seal 3, and protrude for about four and five tenths millimeters (4.5 mm.) into the hollow interior of the lamp envelope, and for purposes of identification will be herein referred to as the lead-in interior section 6, 7. Viewed toward their broad faces, said sections have the form of frustrated isosceles triangles the basal ends whereof may be partly within the pinch. Above the said sections 6, 7 is a coiled filament 8 more specifically identified hereinbelow. Sufiice it to say for the present that the axis of the filament coil lies longitudinally in the plane of said triangles and that the frustrated or obtuse ends of the triangles are, in spacing from the pinch, at a distance which can be here defined as substantially one and three tenths millimeters (1.3 mm.) from the lower level of the coiled filament 8. The said interior in-lead sections 6, 7 may be longitudinally corrugated and/or have curled longitudinal edges both for stiffening purposes and for providing appropriate extensive surface juxtaposition against the wire of which the filament and its reaches are composed, as likewise will subsequently be more specifically explained.

Above-mentioned filament 8, consists essentially of a coil of tungsten wire, the axis of the coil being transverse to the axis of the lamp and overlying, at a distance, the ends of the thin strap-shaped foil in-lead sections 6, 7. The ends of the wire forming the coil extend therefrom in corresponding approximately diametric directions to the coil so as to be parallel to each other at a distance apart thereby being constituted as straight end-reaches 9, 10 adapted to engage the in-lead sections 6, 7 medially between side edges thereof and to be located each in a longitudinal corrugation thereof. Said straight endreaches 9, 10 are longer than said in-lead sections, not only affording the necessary length for spacing the coil of the filament from the ends of the in-leads, but also providing adequate wire length to extend the entire lengths of the interior in-lead sections and onto a portion of the embedded lower sections of said in-leads. At the region of departure of the straight end-reaches 9, 10, permanent attachment may be obtained by use of platinum welds 11, 12. If desired, the lower ends of said straight end-reaches may also be welded to the foil inleads, but in any event, said straight end-reaches are in close juxtaposition to the in-leads, and share in the conduction of electrical current to the forward ends of the in-leads, and consequently will not be brought to incandescence thereat. Furthermore, since the lower portions of the straight end-reaches are embedded in the pinch of the envelope, and upper end portions are welded to the upper ends of the in-leads, and therebetween the said reaches are juxtaposed to the sections 6, 7, respectively, said sections are re-enforced and any bending moment from vibration or otherwise will be distributed longitudinally and will not concentrate, for instance, at point of exit of the wire from the pinch, thereby avoiding metal fatigue and breakage. Mention may also be made that the current is fed to the intermediate foil in-leads by external in-leads or by terminals 13, 14, for instance of molybdenum, welded at lower ends of the intermediate foil in-leads where also embedded in the pinch, said terminals protruding at the lower end of the envelope below the pinch seal.

The lamp contains, besides its halogen gas filling, also an addition of iodine, and the Wattage input on the filament is tuned agreeable to the shape and size of the envelope in such manner that sufficiently high temperatures are attained on the envelope wall to maintain the tungsten iodide cycle. Besides the tungsten of the filament, the molybdenum of the sealed-in foils, and the platinum at the location of the welds, there are no metals present in the lamp which could come into contact with the iodine.

In the actual construction of a lamp embodying the invention, the proportion of length to the diameter of the hollow or interior thereof is generally between the ratio of two to one and one to one (2:1 and 1:1), and the length of the inwardly exposed in-lead section 6, 7 is within the range of fifteen to thirty-five percent (15- 35%) of the length of the interior of the lamp, and the spacing of the ends of the foil sections 6, 7 from the coiled filament is arranged at substantially one to five millimeters (1 to 5 mm.). The proximity of the inner foil sections 6, 7 to the coil filament 8 provides an increment of the reach of the filament wire that will afford appropriate heat transfer to the in-lead sufficient to keep that increment from acquiring as great a temperature as the coil, and thus restrains incandescence from occurring in that increment. By the construction described, therefore, both of the desideratums sought are attained, namely, that the so-called false light or stray light from a lamp intended to produce a single beam, is prevented, and a filament support is provided in which metal fatigue is avoided.

The enumerated advantages may also be attained within the scope of the invention by structural modifications from the specific details elaborated upon in the foregoing description. An example of one such modification is illustrated in FIG. 2. In this showing, a coil filament 22 transversely situated to the axis of the envelope, is provided with straight end-reaches 20, 21, corresponding precisely to the above-described filament 8 and reaches 9, 10 of FIG. 1, with corresponding spacing of the reaches to locate the same longitudinally of and medially between the side edges of respective thin strap in-leads 15, 16 embedded in the lamp press 23. Again it may be said that the upper sections 17, 18 of these in-leads have an isosceles triangular shape with the base of the triangle extending into the pinch 23 along with the lower portions of the straight end-reaches 17, 18 of the filament wire. The construction in FIG. 2 as far as thus described conforms precisely with that of FIG. 1, and all other description given for the first figure also applies here except that the side edges of the tapered portions of the in-leads this time are shown as curled, as at 19, and at the upper portions thereof wrap around the contiguous portions of the end-reaches 20, 21. of the filament wire passing downwardly thereat. Platinum welding may be provided where the wrapping of the foil on the end-reaches occurs. The amount of curl 19 in approach to and into the pinch, may progressively decrease if desired, as shown, rigidity being maintained by virtue of the width of the sections 17, 18 increasing as the curl decreases. The said straight end-reaches are embedded in the pinch and are in close juxtaposition to and physical contact with said foil sections to again accomplish the fatigue-preventing association, and the upper ends have the previously described spacing from the coil to provide the cooling effect and avoid incandescence occurring in the straight end-reaches inclusive of the short increment between the end of the foil and the coil.

We claim:

1. An incandescent halogen electric lamp comprising an envelope having an external pinch-seal with external inlead terminals entering the outer end of said pinch-seal and with wide and thin strap-shaped current conducting intermediate foil inleads joined to the inner end portions of said external inlead terminals and comprising molybdenum foils embedded in said pinch-seal and projecting into the interior hollow of said envelope, and a coiled filament having straight end reaches in abutting relationship to said intermediate molybdenum foil inleads and directed along a substantial length of the portions of said intermediate foil inlead that projects into the interior of said envelope and connected thereto.

2. A lamp is accordance with claim 1, wherein said straight end-reaches of the filament project into said pinch seal and are attached to said intermediate foil in-leads exterior to said pinch-seal and proximate to said coiled filament.

3. A lamp in accordance with claim 2, wherein attachment of said end-reaches to the intermediate foil in-leads is by means of a platinum weld.

4. A lamp in accordance with claim 1, wherein said straight end-reaches of the filament project into said pinchseal and are attached to said intermediate foil in-leads both within and exterior to said seal.

5. A lamp in accordance with claim 4, wherein both of the attachments of the end-reaches to the intermediate foil in-leads are by means of platinum Welds.

6. A lamp in accordance with claim 1, wherein the distance from the coil of the filament to attachment of said end-reaches to the intermediate foil in-leads is of the same order of magnitude as the diameter of the filament coil.

7. A lamp in accordance with claim I, wherein said intermediate foil in-leads have the portions thereof which are nearest to the filament coil in the shape of frustrated isosceles triangles the width whereof diminishes in approach to the vicinity of the coil.

8. A lamp in accordance with claim 1, wherein said straight end-reaches are perpendicular to the axis of the filament coil.

9. A lamp in accordance with claim 8, wherein said envelope has an axial internal length in the same direction as said straight end-reaches in a proportion to the diameter lying between the ratios 2:1 and 1:1, the length of said intermediate foil in-leads within the hollow of the envelope projecting from the pinch-seal are spaced a distance of l to 5 millimeters from the filament coil.

10. A lamp in accordance with claim 1, wherein said filament comprises a wire coil and wherein the thickness of said strap-shaped current conducting intermediate foil in-lead is smaller than the diameter of the filament wire of said coil.

11. A lamp in accordance with claim 1, wherein said intermediate foil in-leads have a generally flat configuration and have restricted portions thereof deviating from the generally flat configuration.

12. A lamp in accordance with claim 11, wherein the portions of the intermediate foil inleads deviating from flat configuration comprises longitudinal corrugations.

13. A lamp in accordance with claim 11, wherein said portions deviating from flat configuration comprises longitudinally curled edges which in part Wrap around said straight end-reaches of the filament, and the curvature of said portions extends at least as far as to the pinchseal.

14-. A lamp in accordance with claim 1, comprising an envelope having an external pinch-seal with Wide and thin strap-shaped current conducting intermediate foil in-leads embedded in said pinch-seal and projecting into the hollow of said envelope, and a coiled filament the axis whereof is transverse to the direction of projection of said intermediate foil in-leads and lies longitudinally substantially in a plane common thereto and to said inintermediate foil in-leads, said filament having straight end-reaches in juxtaposed surface engagement with and attached to said intermediate foil in-leads.

(References on following page) References Cited FOREIGN PATENTS UNITED STATES PATENTS 1,062,008 3/1967 Great Britain.

1,300,688 6/1962 France. 6/1938 Mickley 313-285X 204,640 8/1959 Germany. 3/1953 9 313-415 X 5 JAMES D. KALLAM, Primary Examiner 3/1962 Llngers 313--269X A J JAMES A tE 12/1963 Peek 61; a1 313269 sslsta Xamme 4/1967 Beese 313 31s X us. (:1. X.R. 11/1967 Gates X 10 313-222, 318, 331 

